[TYPO3-english] Get page id and decrease with 1

[Radoslav Kolarov]

Hi All,
I want to get page ID with typoscript and decrease the number with one. 
I get the ID with this code:

temp.value.field = uid

and set prioriCalc to 1
temp.value.prioriCalc = 1

But how to decrease the number? I try some solutions for example:
temp.value = {field:uid} - 1
but it recognize {field:uid} as 0 and the result is -1 :(
Thanks in advance